Process of improving a gun arming efficiency

ABSTRACT

A process is disclosed for assembling a gun tube for use in a perforating system. At a first location, which is not the site where perforating operations are to be conducted, the gun tube is completely assembled except for an initiating device. After transporting the gun tube to the site where perforating operations are to be conducted, an initiator is connected and installed via port in the gun tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to perforating apparatus, and,more particularly, to a process for improving the efficiency with whicha perforating gun is armed.

2. Description of the Prior Art

For purposes of enhancing production from a subterranean formation, aperforating gun typically is lowered down into a wellbore that extendsthrough the formation. A perforating gun may, for example, comprise aplurality of radially-oriented shaped charges which are detonated toform perforations in the formation proximate the wellbore. The shapedcharges may, for example, be placed at points along a helical spiralthat extends around a longitudinal axis of the perforating gun.

Current gun systems use separate components for the pressure bulkhead,detonator, charge holder, detonation cord and wiring to the guns below.When a gun is built, all the pieces are assembled together except thedetonator and shipped to the location where the perforating operation isto be conducted. At that location, the gun is opened and the detonatoris installed. The detonator may, for example, be an RF-safe detonatorprovided by the assignee of the present application, and this detonatormay include an addressable switch, a fireset and an initiator.Accordingly, the installation of the detonator assembly at the sitewhere perforating is to take place involves the connection of a numberof wires in a very small space. The installation of the detonator alsoinvolves the utilization of a safety tube in which the detonator isplaced before connection of the detonator to the wiring in the loadingtube.

It would be advantageous to be able to arm a perforating gun byutilizing a port in the gun assembly thereby avoiding the disassembly ofthe gun components. These novel and useful results have been realized bythe method and apparatus of the present invention.

SUMMARY OF THE INVENTION

In accordance with the present invention, a process is provided forassembling a perforating gun. A process in accordance with the presentinvention comprises installing into a gun tube at a first location (e.g.a workshop, manufacturing site, testing facility or non-field locationthat is not the site at which perforating operations will be conducted)a plurality of shaped charges having primer ends, a ballistics trainincluding a detonating cord connected to the primer ends of the shapedcharges, a detonator receptor that holds a booster and cord in placenear a port, and wiring operatively connected between the ends of thegun tube and to the detonator receptor. One end of the detonating cordis also operatively connected to the detonator receptor. An embodimentof the detonator receptor includes an addressable switch and a firesetand a receptacle for receiving either an exploding foil initiator or anexploding bridge wire detonator. In other embodiments, the detonatorreceptor includes a receptacle for receiving either an exploding foilinitiator or an exploding bridge wire, but does not include anaddressable switch. An addressable switch comprises a circuitfacilitating selection (e.g., from a surface location) of a particularperforating gun in a string of perforating guns. While the detonatorreceptor includes a receptacle for receiving either an exploding foilinitiator or an exploding bridge wire detonator, it is significant thatthe exploding foil initiator or exploding bridge wire is not installedinto the receptacle at the first location. The gun tube thus assembledmay easily be packaged and electrically tested at the first location.

A gun tube thus assembled at the first location is then transported to asecond location, where the second location is the site at which theperforating operation will be conducted (e.g. a field location or otherdeployment site). At the second location, a process in accordance withthe present invention comprises the step of installing an initiatingdevice into the gun tube through a port in the carrier. The initiatingdevice may, for example, be electrically connected to the fireset of thedetonator receptor by a pair of wires through the port while in a safetytube and may then be operatively connected to the detonation cord byinstalling it into the detonator receptor. In one embodiment, theinitiating device comprises an exploding foil initiator, while inanother embodiment the initiating device is an exploding bridge wiredetonator.

In accordance with the present invention, a method of operating aperforating system is provided which comprises assembling a plurality ofgun assemblies as described above and installing the assemblies into acarrier. Each adjacent pair of gun assemblies is separated by a pressurebulkhead. After many gun assemblies and pressure bulkhead as are neededin the perforating operation are assembled into the perforating string,the perforating string may then be lowered into the wellbore and theshaped charges may be detonated.

In accordance with the present invention, a gun tube is provided whichis made in accordance with the process of installing shaped charges, adetonating cord, a detonator receptor and wiring into the gun tube at afirst location which is not the site at which the perforating operationwill be conducted. Apparatus in accordance with the present inventionincludes a gun tube into which an RF-safe or similar detonator isinstalled at the location where the perforating operations are to beconducted.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1-3 are pictorial diagrams in partial cross-section whichillustrates an installation of a detonator into a perforating gunaccording to the prior art.

FIGS. 4-6 are pictorial diagrams in partial cross-section whichillustrate a process in accordance with the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

It will be appreciated that the present invention may take many formsand embodiments. In the following description, some embodiments of theinvention are described and numerous details are set forth to provide anunderstanding of the present invention. Those skilled in the art willappreciate, however, that the present invention may be practiced withoutthose details and that numerous variations and modifications from thedescribed embodiments may be possible. The following description is thusintended to illustrate and not to limit the present invention.

In the specification and appended claims: the terms “connect”,“connection”, “connected”, “in connection with”, and “connecting” areused to mean “in direct connection with” or “in connection with viaanother element”; and the term “set” is used to mean “one element” or“more than one element”. As used herein, the terms “up” and “down”,“upper” and “lower”, “upwardly” and “downwardly”, “upstream” and“downstream”; “above” and “below”; and other like terms indicatingrelative positions above or below a given point or element are used inthis description to more clearly described some embodiments of theinvention. However, when applied to equipment and methods for use inwells that are deviated or horizontal, such terms may refer to a left toright, right to left, or other relationship as appropriate.

In general, the present invention regards improved perforating gunapparatuses and processes of manufacture, assembly, and use for RF-safegun systems. As used herein, the term “RF-safe” means that the initiatorof the gun system is designed to be substantially immune to typicallevels of electrostatic discharge, RF radiation, and/or accidental orunintended applications of power. Moreover, various embodiments of theperforating gun apparatus and processes of manufacture and use aredescribed with respect to selective fire (e.g., wherein the RF-safeinitiator includes an addressable switch). It is intended, however, thatother embodiments of the present invention include improved perforatinggun apparatuses and processes of manufacture, assembly, and use fornon-selective fire gun systems (e.g., wherein the RF-safe initiator doesnot include an addressable switch). In the specification, the term“RF-safe initiating device” is used to mean an exploding foil initiator,an exploding bridge wire detonator, or other component to initiate thegun system in an RF-safe manner. In the specification and appendedclaims, the terms “detonator” and “initiator” may be usedinterchangeably.

With reference to FIGS. 1-3, there is illustrated a process according tothe prior art for installing a detonator 10 in a gun tube 12 at alocation where perforating operations are to be conducted. The size ofdetonator 10 necessitates the removal of end-to-end connections 22 ofadjacent gun assemblies 12 and 20 to install detonator 10 in gun tube12. After end-to-end connections 22 have been removed detonator 10 isplaced in safety tube 18 and the wires 14 are then connected to theleads of the detonator 14. Once wired, detonator 10 may be removed fromsafety tube 18 and installed in the ballistics train by connectingdetonating cord 16 to detonator 10. The end-to-end connections 22 of thegun assemblies 12 and 20 may then be re-established. This prior artmethod of assembling a perforating gun for deployment in the field isinefficient due to the disassembly required.

With reference now to FIGS. 4-6, an embodiment of a gun tube 40 inaccordance with the present invention comprises a detonator receptor 48which could include an addressable switch, a fireset, or simply areceptacle 49 for receiving an RF-safe initiating device, but does notinclude an initiating device. In other embodiments, the detonatorreceptor 48 does not include an addressable switch. The detonatorreceptor 48, along with shaped charges (not shown), wiring 41, anddetonating cord 52 are installed in gun tube tube 40 at a first locationwhich is not the site where perforating operations are to be conducted.The wiring 20 interconnects the ends of the gun tube 44, 40 and isconnected to the detonator receptor 48. The detonating cord 52 isconnected to the primer ends of the shaped charges, and one end ofdetonating cord 52 is operatively connected to detonator receptor 48.All of the components of the detonating apparatus (absent the RF-safeinitiating device) are thus installed at the first location.

Gun tube 40 further comprises a port 42 covered by a removable plug 43.In various embodiments, the plug 43 may be an insertable, threaded, orsliding cover, or any other device to removably obstruct communicationinto the inner bore of the gun tube. At a second location which is thesite at which perforating operations are to be conducted, port 42 isopened and RF-safe initiating device 56 is connected to wires 50 suchthat the RF-safe initiating device is operatively connected to thefireset in the detonator receptor 48. Once wired, RF-safe initiatingdevice 56 may be installed via port 42 into receptacle 49 of detonatorreceptor 48. The installation of RF-safe initiator 56 into detonatorreceptor 48 is such that RF-safe initiating device 56 is operativelyconnected to the detonating cord 52. After installation of the RF-safeinitiating device 56, port 42 is closed again communication into the guntube 40 is interrupted by plug 43.

In some embodiments, the gun tube may comprise a loading tube, or anyother tubular gun housing assembly. Also, in some embodiments, thedetonator receptor may comprise an electronic board.

Embodiments of the perforating gun of the present invention—as describedabove—include apparatuses, processes, and methods wherein a perforatinggun is assembled at a first location that is not the site of perforatingoperations. The “first location” can actually comprise one location thatis not the actual perforating site (i.e., at the well), or alternativelya combination of locations each of which are not the actual perforatingsite. For example, the initiator (without the final RF-safe initiatingdevice) may be manufactured and installed into the gun tube at a shop inChina, and then the gun tube may be transported to a shop in the UnitedStates where the detonating cord and shaped charges are installed andthe gun tube is transported to the well site. At the wellsite, theRF-safe initiating device may be installed via a port in the gun tube.One or more of the guns may be connected together to form an assembledand armed perforating gun string. Finally, the perforating gun stringmay be deployed in the well for detonation downhole.

1. A process for assembling a gun tube with first and second ends foruse in a perforating gun, comprising: installing shaped charges anddetonating cord in the gun tube at a first location which is not wherethe perforating operation will be conducted, the detonating cord beingoperatively connected to the primer ends of the shaped charges; forminga port in the gun tube to permit access to the interior of the gun tube;installing a fireset and detonator receptor adapted to receive aninitiating device into the gun tube proximate said port; and installingwiring into said gun tube at the first location where the wiring isoperatively connected between the ends of the gun tube and to thedetonator receptor..
 2. The process of claim 1, further comprising stepsto be performed at a second location where perforating operations are tobe conducted, the steps comprising: connecting an initiating device tothe fireset of detonator receptor via the port and installing theinitiating device via the port into the gun tube so that the initiatingdevice is in operative connection with one end of the detonating cord;and closing the port.
 3. The process of claim 2, wherein the initiatingdevice is an RF-safe exploding foil initiator.
 4. The process of claim2, wherein the initiating device is an RF-safe exploding bridge wiredetonator.
 5. A gun tube for a perforating gun which is assembled inaccordance with the process of claim
 1. 6. A method of assembling aperforating system, comprising: (a) installing a detonator receptorcomprising an addressable switch and a fireset into a gun tube at afirst location which is not the site of the perforating operation; (b)installing wiring into said gun tube at said first location; (c)installing shaped charges and a detonating cord into the gun tube atsaid first location; (d) repeating steps (a)-(c) for as many gun tubesas are required in the perforating system; (e) transporting the guntubes assembled in steps (a)-(c) to a second location which is the sitewhere perforating operations will be conducted; and (f) installing anRF-safe initiating device into each gun tube at said second locationthrough a port in the gun tube, said RF-safe initiating device, wheninstalled, being operatively connected to said fireset and to saiddetonating cord.
 7. The method of claim 6, wherein the RF-safeinitiating device comprises an exploding bridge wire detonator.
 8. Themethod of claim 6, wherein the RF-safe initiating device comprises anexploding foil initiator.
 9. Apparatus for use in a perforating guncomprising: a gun tube with first and second ends with connectors atsaid ends for receiving shaped charges, a detonating cord and wiring; adetonator receptor comprising a fireset installed in said gun tube at afirst location which is not the site at which perforating operations areto be conducted; wiring which is installed at said first location andwhich is operatively connected between the connectors and to thedetonator receptor; a detonating cord and shaped charges which areinstalled into the gun tube at a said first location, the detonatingcord being operatively connected to the primer ends of the shapedcharges and to the detonator receptor.
 10. The apparatus in claim 9,further comprising an RF-safe initiating device which is installed inthe gun tube via a port in the gun tube at a second location which isthe site of perforating operations.
 11. The gun tube apparatus of claim10, wherein the RF-safe initiating device is selected from a groupconsisting of an exploding bridge wire detonator and an exploding foilinitiator.
 12. The gun tube apparatus of claim 9, wherein the detonatorreceptor further comprises an addressable switch.
 13. A perforatingapparatus for assembly at a first location and for use in a perforatingsystem at a second location, where the first location is not the sitewhere perforating operations will be conducted, comprising: a gun tubehaving an inner bore formed therein and first and second ends andconnectors at each first and second end, the inner bore adapted forreceiving shaped charges, a detonating cord, wiring, and a detonatorreceptor, the gun tube further comprising a port formed therein adaptedto establish communication between the inner bore and external of thegun tube, the detonator receptor comprising an addressable switch and afireset for operative connection to the detonating cord, the detonatorreceptor further comprising a receptacle for receiving a RF-safeinitiating device; a plug adapted to close the port in the gun tube; aplurality of shaped charges having primer ends; a detonating cord forconnection to the primer ends of the shaped charges; and wiring forconnection between the connectors and to the detonator receptor.
 14. Theperforating apparatus of claim 13, wherein the RF-safe initiating deviceis an exploding foil initiator.
 15. The perforating apparatus of claim13, wherein the RF-safe initiating device is an exploding bridge wire.